The present invention relates to a method of judging an immunological reaction, i.e. an antigen-antibody reaction by detecting a pattern formed by particles descending on an inclined bottom surface of a reaction vessel, and also relates to a reaction vessel for use in such a method.
Heretofore, it has been known to judge or determine the antigen-antibody reaction by deliverying an antigen or antibody sample and an antibody or antigen reagent into a reaction vessel having an inclined bottom surface, and then detecting a pattern formed by particles descending on the inclined bottom surface. When there is an antigen-antibody reaction, particles are agglutinated and are deposited uniformly on the inclined bottom surface like snow to form an agglutination pattern. In contrast, when an antigen-antibody reaction does not occur, the particles are not agglutinated and roll down along the inclined bottom surface into the lowermost portion of the reaction vessel to form a non-agglutination pattern.
FIG. 1A illustrates a construction of a microplate 1 which has been used in the known method. The microplate 1 comprises a transparent plate like substrate and a number of reaction vessels 2 formed by depressions arranged in one major surface of the substrate in a matrix form. Each reaction vessel 2 has a conically shaped inclined bottom surface 2a as illustrated in a cross section of FIG. 1B. The reaction vessel 2 may have a round concave bottom surface 2b as illustrated in FIG. 1C. After delivering a sample and a reagent into such a reaction vessel 2, the reaction vessel 2 is kept still for a given time period. Then on the inclined bottom surface of reaction vessel 2 there is formed the aggutinated particle pattern or non-agglutinated particle pattern by means of the particles descending on the bottom surface. Several examples of such particle patterns are depicted in FIG. 2. If an antigen-antibody reaction has taken place in the reaction vessel 2, the particles are agglutinated and are deposited uniformly on the inclined bottom surface. But if an antigen-antibody reaction has not occurred, the particles are not agglutinated with each other and roll down along the inclined bottom surface into the lowermost portion, i.e. the center of the conically inclined bottom surface. Therefore, by detecting the particle pattern formed on the bottom surface of a reaction vessel, it is possible to judge whether or not an antigen-antibody reaction has occurred. However, in the known method, it is difficult to accurately detect intermediate aggutination patterns between the positively agglutinated particle pattern and non-agglutinated particle pattern, due to weak agglutination. Therefore, in the known method it is only possible to judge whether the agglutination has occurred or the agglutination has not occurred.
When checking HB, syphilis, etc., it is necessary to obtain information or data about the degree of agglutination, i.e. the agglutination power, in addition to judging whether the agglutination has occurred or not. Further, some blood subtypes have agglutination powers which differ from one another only slightly. Therefore, in a blood subtype test, there might be misjudgement. Moreover, when detecting the particle pattern photoelectrically, such slightly different particle patterns could not be judged precisely.
In a known method of detecting the agglutination power a sample is diluted by factors of two, four, eight . . . times successively by means of a microtiter to prepare a plurality of diluted samples having different concentrations. Then these differently diluted samples are delivered into successive reaction vessels 2-1, 2-2, 2-3 . . . formed in the microplate 1 as shown in FIG. 3. That is to say, seven diluted samples of a first sample are delivered into seven reaction vessels of a first column A, seven diluted samples of a second sample are delivered into seven reaction vessels of a second column B and so on. At the same time, into seven reaction vessels of a column D are delivered seven diluted samples of a standard sample whose agglutination power is known. After a given time period, particle patterns formed on the bottom surfaces of reaction vessels 2-1, 2-2 . . . 2-7 are compared with standard particle patterns formed on the bottom surfaces of reaction vessels belonging to column D. In this manner, values or indices of the agglutination power of unknown samples can be detected. In this method, even if the agglutination power is relatively small, the judgement can be effected precisely. However, in the known method, since it is necessary to deliver the differently diluted samples into the reaction vessels, the process could not be carried out efficiently. Particularly, if the concentrations of the diluted samples are not correct, judging accuracy is greatly affected resulting in a decrease of reliability. Further, the method requires inherently larger amounts of sample and reagent, and thus the running cost is liable to be increased.